From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755260Ab1CQSr2 (ORCPT ); Thu, 17 Mar 2011 14:47:28 -0400 Received: from mail-px0-f179.google.com ([209.85.212.179]:64717 "EHLO mail-px0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754968Ab1CQSrZ (ORCPT ); Thu, 17 Mar 2011 14:47:25 -0400 Date: Thu, 17 Mar 2011 12:47:23 -0600 From: Grant Likely To: David Daney Cc: Alan Cox , linux-serial@vger.kernel.org, gregkh@suse.de, linux-kernel@vger.kernel.org, devicetree-discuss@lists.ozlabs.org Subject: Re: [RFC PATCH 1/2] serial: 8250: Add a notifier chain for driver registration. Message-ID: <20110317184723.GQ9597@angua.secretlab.ca> References: <1300325167-26433-1-git-send-email-ddaney@caviumnetworks.com> <1300325167-26433-2-git-send-email-ddaney@caviumnetworks.com> <20110317121849.49d7c425@lxorguk.ukuu.org.uk> <20110317182510.GN9597@angua.secretlab.ca> <4D82560B.4090800@caviumnetworks.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4D82560B.4090800@caviumnetworks.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 17, 2011 at 11:42:19AM -0700, David Daney wrote: > On 03/17/2011 11:25 AM, Grant Likely wrote: > >On Thu, Mar 17, 2011 at 12:18:49PM +0000, Alan Cox wrote: > >>On Wed, 16 Mar 2011 18:26:06 -0700 > >>David Daney wrote: > >> > >>>The 8250 driver is a bit weird in that in addition to supporting > >>>platform devices, extra devices can be added by calling > >>>serial8250_register_port(). > >>> > >>>The problem is that if we call serial8250_register_port() before the > >>>driver is initialized Bad Things happen (we dereference NULL > >>>pointers). > >>> > >>>There doesn't seem to be a general way to know if a driver has been > >>>initialized > >> > >>I've had a bigger dig into this. I think the correct answer is probably > >>"always go via platform devices or similar". That *is* the notifier in > >>the kernel of today. serial8250_register_port ultimately should I think > >>ultimatly become an internal helper. > > > >+1 > > > >Depending on serial8250_register_port() definitely the wrong thing to > >do for platform support code. It would be better to figure out how to > >get the dt bits you need into 8250.c or of_serial.c. > > > > IMHO, of_serial.c is no better than my board/chip specific code that > calls serial8250_register_port(). > > Really what would be ideal would be a hook to add a > dev.platform_data pointer to the appropriate struct > plat_serial8250_port when the platform device is created. It is > possible that the platform bus notifiers could be used for this. We > would also want to have a way to add an of_device_id to those > recognized by 8250.c > > If we did that, serial8250_probe() would automatically do the right thing. Take a look at the way arch/powerpc/platforms/512x/pdm360ng.c uses a notifier for amending a platform_device with additional data.. g.